This gene encodes a sucrase-isomaltase enzyme that is expressed in the intestinal brush border. The encoded protein is synthesized as a precursor protein that is cleaved by pancreatic proteases into two enzymatic subunits sucrase and isomaltase. These two subunits heterodimerize to form the sucrose-isomaltase complex. This complex is essential for the digestion of dietary carbo... See more...

Aliases for SI Gene

Aliases for SI Gene

  • Sucrase-Isomaltase 2 3 5
  • Oligosaccharide Alpha-1,6-Glucosidase 2 3
  • Sucrase-Isomaltase, Intestinal 3 4
  • Alpha-Methylglucosidase 2 3
  • Oligo-1,6-Glucosidase 2 3
  • Alpha-Glucosidase 2 3
  • Sucrase-Isomaltase (Alpha-Glucosidase) 2
  • EC 50
  • SI 5

External Ids for SI Gene

Previous GeneCards Identifiers for SI Gene

  • GC03M161906
  • GC03M165752
  • GC03M166071
  • GC03M166017
  • GC03M166179
  • GC03M164696
  • GC03M162066

Summaries for SI Gene

Entrez Gene Summary for SI Gene

  • This gene encodes a sucrase-isomaltase enzyme that is expressed in the intestinal brush border. The encoded protein is synthesized as a precursor protein that is cleaved by pancreatic proteases into two enzymatic subunits sucrase and isomaltase. These two subunits heterodimerize to form the sucrose-isomaltase complex. This complex is essential for the digestion of dietary carbohydrates including starch, sucrose and isomaltose. Mutations in this gene are the cause of congenital sucrase-isomaltase deficiency.[provided by RefSeq, Apr 2010]

GeneCards Summary for SI Gene

SI (Sucrase-Isomaltase) is a Protein Coding gene. Diseases associated with SI include Sucrase-Isomaltase Deficiency, Congenital and Pneumatosis Cystoides Intestinalis. Among its related pathways are Glycosaminoglycan metabolism and Galactose metabolism. Gene Ontology (GO) annotations related to this gene include carbohydrate binding and alpha-1,4-glucosidase activity. An important paralog of this gene is MGAM.

UniProtKB/Swiss-Prot Summary for SI Gene

  • Plays an important role in the final stage of carbohydrate digestion. Isomaltase activity is specific for both alpha-1,4- and alpha-1,6-oligosaccharides.

No data available for CIViC Summary , Tocris Summary , Gene Wiki entry , PharmGKB "VIP" Summary , Rfam classification and piRNA Summary for SI Gene

Genomics for SI Gene

GeneHancer (GH) Regulatory Elements Pubs

Promoters and enhancers for SI Gene
GeneHancer (GH) Identifier GH Type GH
GH Sources Gene Association Score Total Score TSS distance (kb) Number of Genes Away Size (kb) Transcription Factor
Binding Sites
Gene Targets
GH03J165078 Promoter 0.3 EPDnew 250.7 0.0 -20 0.1 SI LOC105374192 RF00998-097 HSALNG0030413 SLITRK3
GH03J165128 Enhancer 0.8 ENCODE 11.1 -53.1 -53101 5.9 CEBPA YY1 HOMEZ FOXA2 KDM6A SMAD4 RXRA SAP130 RARA JUND SI ENSG00000200052 LINC02023 SLITRK3
GH03J165071 Enhancer 0.3 FANTOM5 0.4 +6.6 6570 0.2 RFX1 LOC105374192 SI HSALNG0030414 HSALNG0030413
GH03J165195 Promoter 1.1 EPDnew Ensembl 0.1 -118.1 -118104 2 YY1 REST ZNF398 ZNF366 L3MBTL2 PKNOX1 EGR2 EZH2 CBX8 ZBTB17 HSALNG0030419 SLITRK3 HSALNG0030418 SI
GH03J165192 Promoter/Enhancer 0.9 Ensembl ENCODE 0.1 -115.3 -115291 3.2 POLR2A SIN3A YY1 TAF1 SP1 ZNF384 PKNOX1 NANOG EZH2 CBX8 HSALNG0030418 SLITRK3 SI
- Elite GeneHancer and/or Elite GeneHancer-gene association Download GeneHancer data from 2017 publication | Request up-to-date GeneHancer data (full dataset)

GeneHancers around SI on the GeneHancer Hub at the UCSC Golden Path

Cistromic (ChIP-Seq) regulation report from SPP (The Signaling Pathways Project) for SI

Top Transcription factor binding sites by QIAGEN in the SI gene promoter:
  • AP-1
  • ATF-2
  • NF-kappaB
  • NF-kappaB1
  • SRY
  • TBP

Genomic Locations for SI Gene

Latest Assembly
99,599 bases
Minus strand

Previous Assembly
(GRCh37/hg19 by Entrez Gene)
99,599 bases
Minus strand

(GRCh37/hg19 by Ensembl)
99,598 bases
Minus strand

Genomic View for SI Gene

Genes around SI on UCSC Golden Path with GeneCards custom track

Cytogenetic band:
SI Gene in genomic location: bands according to Ensembl, locations according to GeneLoc (and/or Entrez Gene and/or Ensembl if different)
Genomic Location for SI Gene
GeneLoc Logo Genomic Neighborhood Exon StructureGene Density

RefSeq DNA sequence for SI Gene

Proteins for SI Gene

  • Protein details for SI Gene (UniProtKB/Swiss-Prot)

    Protein Symbol:
    Recommended name:
    Sucrase-isomaltase, intestinal
    Protein Accession:
    Secondary Accessions:
    • A2RUC3
    • Q1JQ80
    • Q1RMC2

    Protein attributes for SI Gene

    1827 amino acids
    Molecular mass:
    209453 Da
    Quaternary structure:
    • The resulting sucrase and isomaltase subunits stay associated with one another in a complex by non-covalent linkages.
    • There is a high degree of homology between the isomaltase and sucrase portions (41% of amino acid identity) indicating that this protein is evolved by partial gene duplication.

    Three dimensional structures from OCA and Proteopedia for SI Gene

neXtProt entry for SI Gene

Selected DME Specific Peptides for SI Gene


Post-translational modifications for SI Gene

  • The precursor is proteolytically cleaved when exposed to pancreatic proteases in the intestinal lumen.
  • Sulfated.
  • Glycosylation at Asn99, Asn437, Asn455, Asn823, Asn855, Asn904, Asn926, Asn1235, Asn1303, Asn1340, Asn1354, Asn1403, Asn1535, Asn1572, Asn1675, Asn1748, Asn1763, and Asn1815
  • Modification sites at PhosphoSitePlus

Other Protein References for SI Gene

Antibodies for research

  • Abcam antibodies for SI
  • Invitrogen Antibodies for SI (AFLGC-SI)

Domains & Families for SI Gene

Gene Families for SI Gene

Human Protein Atlas (HPA):
  • Disease related genes
  • Enzymes
  • FDA approved drug targets
  • Plasma proteins
  • Predicted membrane proteins

Protein Domains for SI Gene

Suggested Antigen Peptide Sequences for SI Gene

GenScript: Design optimal peptide antigens:
  • Sucrase-isomaltase, intestinal (SUIS_HUMAN)

Graphical View of Domain Structure for InterPro Entry



  • Belongs to the glycosyl hydrolase 31 family.
  • Belongs to the glycosyl hydrolase 31 family.
genes like me logo Genes that share domains with SI: view

Function for SI Gene

Molecular function for SI Gene

UniProtKB/Swiss-Prot Function:
Plays an important role in the final stage of carbohydrate digestion. Isomaltase activity is specific for both alpha-1,4- and alpha-1,6-oligosaccharides.
UniProtKB/Swiss-Prot CatalyticActivity:
Reaction=Hydrolysis of sucrose and maltose by an alpha-D-glucosidase-type action.; EC=;.
UniProtKB/Swiss-Prot CatalyticActivity:
Reaction=Hydrolysis of (1->6)-alpha-D-glucosidic linkages in some oligosaccharides produced from starch and glycogen by alpha-amylase, and in isomaltose.; EC=;.
GENATLAS Biochemistry:
sucrase-isomaltase,alpha D-glucosidase from intestinal mucosa that hydrolyzes sucrose and isomaltose,member of the glycosyl hydrolase family 3

Enzyme Numbers (IUBMB) for SI Gene

Phenotypes From GWAS Catalog for SI Gene

Gene Ontology (GO) - Molecular Function for SI Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0003824 catalytic activity IEA --
GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds IBA 21873635
GO:0004558 alpha-1,4-glucosidase activity IBA 21873635
GO:0004574 oligo-1,6-glucosidase activity IEA --
GO:0004575 sucrose alpha-glucosidase activity TAS --
genes like me logo Genes that share ontologies with SI: view
genes like me logo Genes that share phenotypes with SI: view

Human Phenotype Ontology for SI Gene

HPO Id HPO Name Alternative Ids Definition Synonyms

miRNA for SI Gene

miRTarBase miRNAs that target SI

Inhibitory RNAs for research

  • Search GeneCopoeia for shRNA, lentivirus and/or AAV clone products for SI

No data available for Animal Models , Transcription Factor Targets and HOMER Transcription for SI Gene

Localization for SI Gene

Subcellular locations from UniProtKB/Swiss-Prot for SI Gene

Apical cell membrane. Single-pass type II membrane protein. Note=Brush border.

Subcellular locations from

Extracellular space Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi Apparatus Nucleus Mitochondrion 0 1 2 3 4 5 Confidence
COMPARTMENTS Subcellular localization image for SI gene
Compartment Confidence
plasma membrane 5
extracellular 5
golgi apparatus 4
endoplasmic reticulum 3
cytosol 3
lysosome 3
cytoskeleton 2
mitochondrion 2
peroxisome 2
nucleus 2
endosome 1

Gene Ontology (GO) - Cellular Components for SI Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0005794 Golgi apparatus TAS 1717481
GO:0005886 plasma membrane TAS --
GO:0005903 brush border TAS 1717481
GO:0016020 membrane IEA --
GO:0016021 integral component of membrane IEA --
genes like me logo Genes that share ontologies with SI: view

No data available for Subcellular locations from the Human Protein Atlas (HPA) for SI Gene

Pathways & Interactions for SI Gene

genes like me logo Genes that share pathways with SI: view

Gene Ontology (GO) - Biological Process for SI Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0005975 carbohydrate metabolic process IEA --
GO:0008152 metabolic process IEA --
GO:0044245 polysaccharide digestion TAS --
genes like me logo Genes that share ontologies with SI: view

No data available for SIGNOR curated interactions for SI Gene

Drugs & Compounds for SI Gene

(42) Drugs for SI Gene - From: DrugBank, DGIdb, HMDB, and Novoseek

Name Status Disease Links Group Role Mechanism of Action Clinical Trials
Acarbose Approved, Investigational Pharma Target, inhibitor Alpha-glucosidase inhibitor, Glucosidase alpha inhibitor (intestinal) 102
Sucrose Approved, Experimental, Investigational Pharma 0
Scopolamine Approved, Investigational Pharma Target, inhibitor 116
D-glucose Approved, Experimental, Investigational, Vet_approved Pharma 0
Water Approved Pharma 0

(27) Additional Compounds for SI Gene - From: HMDB and Novoseek

Name Synonyms Role CAS Number PubChem IDs PubMed IDs
  • 6-O-alpha-D-Glucopyranosyl-D-glucose
  • 6-O-alpha-D-Glucopyranosyl-beta-D-glucopyranose
  • 6-O-Α-D-glucopyranosyl-D-glucose
  • 6-O-Α-D-glucopyranosyl-β-D-glucopyranose
  • D-Isomaltose
  • alpha-D-GLC
  • alpha-Dextrose
  • a-D-GLC
  • Α-D-GLC
  • a-Dextrose
  • British gum
  • Caloreen
  • Corn dextrin
  • Crystal gum
  • Dextrid
  • beta-D-Arabino-hexulose
  • beta-D-Fructose
  • beta-Fruit sugar
  • beta-Levulose
genes like me logo Genes that share compounds with SI: view

Transcripts for SI Gene

mRNA/cDNA for SI Gene

11 NCBI additional mRNA sequence :
3 Ensembl transcripts including schematic representations, and UCSC links to gene/alias where relevant :

Inhibitory RNAs for research

  • Search GeneCopoeia for shRNA, lentivirus and/or AAV clone products for SI

Alternative Splicing Database (ASD) splice patterns (SP) for SI Gene

ExUns: 1 ^ 2 ^ 3a · 3b · 3c ^ 4 ^ 5 ^ 6 ^ 7 ^ 8 ^ 9 ^ 10 ^ 11 ^ 12 ^ 13 ^ 14 ^ 15 ^ 16 ^ 17 ^ 18 ^ 19 ^ 20 ^ 21a · 21b ^ 22a · 22b ^
SP1: - -
SP2: -
SP7: -

ExUns: 23 ^ 24 ^ 25 ^ 26 ^ 27 ^ 28 ^ 29 ^ 30 ^ 31 ^ 32 ^ 33

Relevant External Links for SI Gene

GeneLoc Exon Structure for

Expression for SI Gene

mRNA expression in normal human tissues from GTEx, Illumina, BioGPS, and SAGE for SI Gene

mRNA expression in embryonic tissues and stem cells from LifeMap Discovery

mRNA differential expression in normal tissues according to GTEx for SI Gene

This gene is overexpressed in Small Intestine - Terminal Ileum (x46.9) and Colon - Transverse (x4.6).

Protein differential expression in normal tissues from HIPED for SI Gene

This gene is overexpressed in Pancreatic juice (58.8) and Fetal gut (10.1).

Integrated Proteomics: protein expression in normal tissues and cell lines from ProteomicsDB, MaxQB, and MOPED for SI Gene

Protein tissue co-expression partners for SI Gene

- Elite partner

Transcriptomic regulation report from SPP (The Signaling Pathways Project) for SI

SOURCE GeneReport for Unigene cluster for SI Gene:


mRNA Expression by UniProt/SwissProt for SI Gene:

Tissue specificity: Expressed in the poorly differentiated crypt cells of the small intestine as well as in the mature villous cells. Expressed at very low levels in the colon.

Evidence on tissue expression from TISSUES for SI Gene

  • Intestine(4.7)
  • Nervous system(4.5)
  • Pancreas(3.5)
  • Muscle(3.1)
  • Liver(2.9)
  • Kidney(2.5)
  • Blood(2.5)
  • Heart(2.1)
  • Lung(2.1)
  • Urine(2)

Phenotype-based relationships between genes and organs from Gene ORGANizer for SI Gene

Germ Layers:
  • endoderm
  • mesoderm
  • digestive
  • urinary
  • intestine
  • kidney
  • large intestine
  • small intestine
  • ureter
genes like me logo Genes that share expression patterns with SI: view

Primer products for research

Orthologs for SI Gene

This gene was present in the common ancestor of animals.

Orthologs for SI Gene

Organism Taxonomy Gene Similarity Type Details
(Pan troglodytes)
Mammalia SI 29 30
  • 99.4 (n)
(Canis familiaris)
Mammalia SI 29 30
  • 87.53 (n)
(Bos Taurus)
Mammalia SI 29 30
  • 86.41 (n)
(Mus musculus)
Mammalia Sis 29 16 30
  • 79.88 (n)
(Rattus norvegicus)
Mammalia Si 29
  • 77.38 (n)
(Monodelphis domestica)
Mammalia SI 30
  • 73 (a)
(Ornithorhynchus anatinus)
Mammalia SI 30
  • 68 (a)
(Gallus gallus)
Aves -- 30
  • 48 (a)
-- 30
  • 39 (a)
(Anolis carolinensis)
Reptilia -- 30
  • 50 (a)
-- 30
  • 44 (a)
-- 30
  • 42 (a)
(Danio rerio)
Actinopterygii CU914772.1 30
  • 37 (a)
wufd44a09 29
(Caenorhabditis elegans)
Secernentea D2096.3 31
  • 38 (a)
R05F9.12 31
  • 36 (a)
F53F4.8 31
  • 35 (a)
aagr-1 30
  • 34 (a)
aagr-2 30
  • 33 (a)
Sea Squirt
(Ciona savignyi)
Ascidiacea -- 30
  • 44 (a)
-- 30
  • 40 (a)
Species where no ortholog for SI was found in the sources mined by GeneCards:
  • A. gosspyii yeast (Eremothecium gossypii)
  • Actinobacteria (Mycobacterium tuberculosis)
  • African clawed frog (Xenopus laevis)
  • African malaria mosquito (Anopheles gambiae)
  • Alicante grape (Vitis vinifera)
  • Alpha proteobacteria (Wolbachia pipientis)
  • Amoeba (Dictyostelium discoideum)
  • Archea (Pyrococcus horikoshii)
  • Baker's yeast (Saccharomyces cerevisiae)
  • Barley (Hordeum vulgare)
  • Beta proteobacteria (Neisseria meningitidis)
  • Bread mold (Neurospora crassa)
  • Chromalveolata (Phytophthora infestans)
  • Common water flea (Daphnia pulex)
  • Corn (Zea mays)
  • E. coli (Escherichia coli)
  • Filamentous fungi (Aspergillus nidulans)
  • Firmicute Bacteria (Streptococcus pneumoniae)
  • Fission Yeast (Schizosaccharomyces pombe)
  • Fruit Fly (Drosophila melanogaster)
  • Green Algae (Chlamydomonas reinhardtii)
  • Honey Bee (Apis mellifera)
  • K. Lactis Yeast (Kluyveromyces lactis)
  • Loblloly Pine (Pinus taeda)
  • Malaria Parasite (Plasmodium falciparum)
  • Medicago Trunc (Medicago Truncatula)
  • Moss (Physcomitrella patens)
  • Orangutan (Pongo pygmaeus)
  • Pig (Sus scrofa)
  • Rainbow Trout (Oncorhynchus mykiss)
  • Rice (Oryza sativa)
  • Rice Blast Fungus (Magnaporthe grisea)
  • Schistosome Parasite (Schistosoma mansoni)
  • Sea Anemone (Nematostella vectensis)
  • Sea Vase (Ciona intestinalis)
  • Sea Urchin (Strongylocentrotus purpuratus)
  • Sorghum (Sorghum bicolor)
  • Soybean (Glycine max)
  • Stem Rust Fungus (Puccinia graminis)
  • Sugarcane (Saccharum officinarum)
  • Thale Cress (Arabidopsis thaliana)
  • Tomato (Lycopersicon esculentum)
  • Toxoplasmosis (Toxoplasma gondii)
  • Trichoplax (Trichoplax adhaerens)
  • Tropical Clawed Frog (Silurana tropicalis)
  • Wheat (Triticum aestivum)

Evolution for SI Gene

Gene Tree for SI (if available)
Gene Tree for SI (if available)
Evolutionary constrained regions (ECRs) for SI: view image
Alliance of Genome Resources:
Additional Orthologs for SI

Paralogs for SI Gene

Paralogs for SI Gene

(2) SIMAP similar genes for SI Gene using alignment to 2 proteins:

  • F8WF21_HUMAN Pseudogenes for SI Gene

genes like me logo Genes that share paralogs with SI: view

Variants for SI Gene

Sequence variations, with clinical significance, from ClinVar and Humsavar, with links to dbSNP for SI Gene

SNP ID Clinical significance and condition Chr 03 pos Variation AA Info Type
1019910 Uncertain Significance: not provided 165,032,665(-) A/C
NM_001041.4(SI):c.2593T>G (p.Ser865Ala)
1032567 Pathogenic: Sucrase-isomaltase deficiency 165,039,119(-) TCA/T
NM_001041.4(SI):c.2258_2259del (p.Val753fs)
1032568 Pathogenic: Sucrase-isomaltase deficiency 165,009,305(-) T/A
NM_001041.4(SI):c.4153A>T (p.Lys1385Ter)
1032569 Pathogenic: Sucrase-isomaltase deficiency 165,068,720(-) A/G
1032570 Pathogenic: Sucrase-isomaltase deficiency 164,979,400(-) CAT/C
NM_001041.4(SI):c.5444_5445del (p.Asn1815fs)

dbSNP identifiers (rs#s) for variants without ClinVar clinical significance for SI Gene

All consequence types are included: molecular consequences (e.g. missense, synonymous), and location-based (e.g. intron, upstream).

Structural Variations from Database of Genomic Variants (DGV) for SI Gene

Variant ID Type Subtype PubMed ID
dgv8717n54 CNV loss 21841781
esv2577226 CNV deletion 19546169
esv2763324 CNV gain 21179565
esv3569104 CNV loss 25503493
esv3575627 CNV gain 25503493
nsv1013393 CNV loss 25217958
nsv1014800 CNV gain 25217958
nsv1161003 CNV duplication 26073780
nsv428426 CNV loss 18775914
nsv518452 CNV loss 19592680
nsv592446 CNV loss 21841781
nsv592450 CNV gain 21841781
nsv829785 CNV loss 17160897

Variation tolerance for SI Gene

Residual Variation Intolerance Score: 2% of all genes are more intolerant (likely to be disease-causing)
Gene Damage Index Score: 9.89; 89.75% of all genes are more intolerant (likely to be disease-causing)

Additional Variant Information for SI Gene

Human Gene Mutation Database (HGMD)
SNPedia medical, phenotypic, and genealogical associations of SNPs for
Leiden Open Variation Database (LOVD)

SNP Genotyping and Copy Number Assays for research

No data available for Polymorphic Variants from UniProtKB/Swiss-Prot for SI Gene

Disorders for SI Gene

MalaCards: The human disease database

(36) MalaCards diseases for SI Gene - From: OMI, CVR, GTR, ORP, SWI, COP, and GCD

Disorder Aliases PubMed IDs
sucrase-isomaltase deficiency, congenital
  • csid
pneumatosis cystoides intestinalis
  • diarrhea of presumed infectious origin
hirata disease
  • insulin autoimmune syndrome
glycogen storage disease ii
  • gsd2
- elite association - COSMIC cancer census association via MalaCards
Search SI in MalaCards View complete list of genes associated with diseases


  • Congenital sucrase-isomaltase deficiency (CSID) [MIM:222900]: Autosomal recessive intestinal disorder that is clinically characterized by fermentative diarrhea, abdominal pain, and cramps upon ingestion of sugar. The symptoms are the consequence of absent or drastically reduced enzymatic activities of sucrase and isomaltase. The prevalence of CSID is 0.02 % in individuals of European descent and appears to be much higher in Greenland, Alaskan, and Canadian native people. CSID arises due to post-translational perturbations in the intracellular transport, polarized sorting, aberrant processing, and defective function of SI. {ECO:0000269 PubMed:10903344, ECO:0000269 PubMed:11340066, ECO:0000269 PubMed:14724820, ECO:0000269 PubMed:16329100, ECO:0000269 PubMed:8609217}. Note=The disease is caused by variants affecting the gene represented in this entry.

Genatlas disease for SI Gene

disaccharide intolerance

Additional Disease Information for SI

genes like me logo Genes that share disorders with SI: view

Publications for SI Gene

  1. Congenital sucrase-isomaltase deficiency. Identification of a glutamine to proline substitution that leads to a transport block of sucrase-isomaltase in a pre-Golgi compartment. (PMID: 8609217) Ouwendijk J … Naim HY (The Journal of clinical investigation 1996) 3 4 22 72
  2. Sequence of the complete cDNA and the 5' structure of the human sucrase-isomaltase gene. Possible homology with a yeast glucoamylase. (PMID: 1353958) Chantret I … Rousset M (The Biochemical journal 1992) 2 3 4 22
  3. Structural basis for substrate selectivity in human maltase-glucoamylase and sucrase-isomaltase N-terminal domains. (PMID: 20356844) Sim L … Rose DR (The Journal of biological chemistry 2010) 3 4 22
  4. Novel mutations in the human sucrase-isomaltase gene (SI) that cause congenital carbohydrate malabsorption. (PMID: 16329100) Sander P … Naim HY (Human mutation 2006) 3 4 22
  5. Congenital sucrase-isomaltase deficiency because of an accumulation of the mutant enzyme in the endoplasmic reticulum. (PMID: 14724820) Ritz V … Naim HY (Gastroenterology 2003) 3 4 22

Products for SI Gene

Sources for SI Gene